MX2011010720A - Efficient uplink transmission of channel state information. - Google Patents

Abstract

A UE in a wireless communication network transmits succinct, direct channel state information to the network, enabling coordinated multipoint calculations such as joint processing, without substantially increasing uplink overhead. The UE receives and processes reference symbols over a set of non-uniform!y spaced sub-carriers, selected according to a scheme synchronized to the network. The frequency response for each selected sub- carrier is estimated conventionally, and the results quantized and transmitted to the network on an uplink control channel. The non-uniform sub-carrier selection may be synchronized to the network in a variety of ways.

Description

TRANSFER OF EFFICIENT ASCENDING LINK OF INFORMATION FROM THE STATE OF THE CHANNEL TECHNICAL FIELD The present invention relates generally to wireless communications in particular to an efficient system and method for providing channel state information of the user equipment to a wireless communication network.

BACKGROUND This application claims priority to the Provisional Patent Application of E.U.A. Series No. 61 / 172,484, filed on April 24, 2009, entitled "Information Feedback on Cannibal Status by Digital Interception" and here incorporated by reference in its entirety.

The wireless communication networks transmit communication signals in the downlink over the radio frequency channels of the fixed transceivers, known as base stations, to the mobile user equipment (UE) within a geographical area, or cell. The UE transmission signals in the uplink to na or more base stations. In both cases, the received signal can be characterized as the transmitted signal, altered by channel effects, more noise and interference. In order to recover the transmitted signal from a received signal, a receiver therefore requires an estimate of the channel and an estimate of the noise / interference. The characterization of a channel is known as channel state information (CSI). A known way of estimating a channel is to periodically transmit known reference symbols, also known as pilot symbol. Since the reference symbols1 are known by the receiver, any deviation in the symbols received from the reference symbols (once the estimated noise / interference is removed) is caused by channel effects. An accurate estimate of CSI allows a receiver to more accurately recover the signals transmitted from the received signals. In addition, by transmitting CSI from the reiceptor to a transmitter, the transmitter may select the transmission characteristics - such as coding, modulation and the like, best studied for the current channel state. It is known that the adaptation 3 link dependent channel.

Modern wireless communication networks have limited interference. Networks normally process transmissions directed to each UE in a cell independently. Transmissions to other UEs in the same cell are considered as interference to a given UE giving rise to the inter-cell interference term. Uft effort to mitigate the interference between cells is the transmission of Multiple Points Coordinated (CoMP). CoMP systems employ numerous techniques to mitigate inter-cell interference, including MIMO channels, numerous distributed antennas, beamforming and splice processes.

Empalmes processes (JP, for its acronym in English) is a transmission technique of CoMP that is currently studied for Long Term Evolution (LTE, for its acronym in English). In JP, transmissions to multiple UEs are considered together and a global optimization algorithm is applied to reduce interference between cells. That is, the JP algorithms try to direct the transmission energy towards destination UE, while avoiding the generation of interference in other UEs. To operate effectively, JP systems require information about the transmission channels. There are two forms in which the channel information, or CSI, is fed back to the transmitters of the system: Pre-coding Matrix Indicator (PMI) and quantized channel feedback.

The PMI feedback, specified in the LTE Release 8, is essentially a recommendation of a transmission format for each UE. A plurality of previously defined pre-coding matrices are designed offline and are known in the base station and UE. The precoding matrices define several downlink coding groups and transmission parameters. Each UE measures its channel and searches through the precoding matrices, selecting one that optimizes some quantifiable metric. The selected precoding matrix is fed again or the base station is reported. The base station then considers all the recommended precoding matrices and selects the precoding and transmission parameters that implement a globally optimal solution on the cell. In the scenarios contemplated when the 9 LTE Release is designated, the PMI feedback works well, due to a high correlation between the U $ recommendations and the actual convenient transmission parameters. PMI feedback compression reduces the uplink walk width by exploiting the fact that only part of the channel, "strong directions", ie the signal space-needs to be fed back to the transmitter.

In JO CoMP applications, it is unlikely that the desired transmission format (which achieves suppression of interference) will match a transmission format recommended by a UE If the recommendation UE has any • recognition about other UEs that will be interfered with by the UE. transmission to the recommendation EU. Additionally, the recommendation UE is not aware of the transmissions programmed to other UEs that will interfere with their signals. Also, the PMI feedback compression reduces the bandwidth by reporting only the part of the channel of interest to the transmissions addressed to UE re recommendation UE. While this increases the uplink efficiency for non-cooperative transmission, it is disadvantageous for cooperative transmission, since it negates the network information about the channel that may be useful in JP optimization.

In the quantized channel feedback, the UE attempt describes the real channel. In contrast to the PMI feedback, this encompasses the feed-feedback information about not only the signal space but also the complementary space (the "weakening space", also called something not precisely referred to as the "null space") of the channel . The feedback of the entire channel results in several advantages. With full CSI in the network, consistent JP schemes can suppress interference. Additionally, the network can obtain individualized channel feedback by transmitting unique reference symbols for each UE. This allows for flexible implementations and future testing of a variety of JP transmission methods, since the methods are essentially transparent to the UE.

Even without the CoMP transmission of JP, CSI eh the network can solve one of the most fundamental problems that plagued the current wireless system - the inaccuracy in channel dependent link adaptation because the network can not predict the interference experienced by the network. UE (a problem closely related to the well-known instantaneous light effect). Once the network knows the CSI of the bases near each UE, the network can accurately predict the SINR in each UE that results in the link adaptation significantly more accurate.

Although the benefits of CSI directly over P I feedback are clear, the main aspect with direct CSI feedback is bandwidth. Full CSI feedback requires a high transfer rate to transmit the CSI of each UE to the network. The time-frequency uplink channel resources shall be used to carry the CSI feedback in the uplink channel, making these resources not available to transmit user data in the uplink, the CSI feedback transmissions therefore they are superiorly pure, thus directly reducing the efficiency of uplink data transmissions. The direct CSI feedback transport to the network without consuming excessive uplink resources was established as a Main confrontation of modern communication system design.

SUMMARY According to one or more modalities described and claimed herein, a UE in a wireless communication network conveys concisely the direct channel state information to the network, allowing calculations of multiple points in the coordinates such as splicing process, without substantially increase the upper uplink. UE receives and processes reference symbols on a set of subcarriers separated non-uniformly, selected according to a scheme synchronized to the network. The frequency response for each selected subcarrier is conventionally estimated and the results quantified and transmitted to the network in an uplink control channel. The non-uniform subcarrier selection can be synchronized to the network in a variety of ways.

One embodiment refers to a method for reporting the channel status information by a UE operative in a wireless communication network in which the downlink data is modulated into a plurality of subcarriers, each having a different frequency. A plurality of known reference symbols is received on a subgroup of the plurality of subcarriers. A group of Separate subcarriers are not uniformly selected using a selection scheme synchronized to the network. A frequency response is estimated for each selected subcarrier. The frequency responses are quantified and transmitted to the network via an uplink control channel.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a functional block diagram of a wireless communication network.

Figure 2A is a time-frequency graph showing transmission of the reference symbol of a single antenna port.

Figure 2B is a reference symbol transmission showing the time frequency graph of two antenna ports.

Figure 2C is a time-frequency graph showing the reference symbol transmission of three antenna ports.

Figure 3 is a flowchart of a method for reporting CSI feedback by a UE.

Figure 4A is a graph of the in-phase component of a representative channel response, describing the estimates of the quantized channel reported to the network.

Figure 4B is a graph of the quadrature component of a representative channel response, describing the quantified channel estimates reported to the network.

DETAILED DESCRIPTION For purposes of the clear description and full enablement, the present invention is described as being modalized in a wireless communication network based on the modulation of the Orthogonal Frequency Division Multiplex (OFDM). More specifically, the present modalities are based on the Universal Terrestrial Radio Access (E-UTRA) system, which is also commonly referred to as the Long-Term Evolution (LOTE) of widely deployed WCDMA systems. . Those skilled in the art will readily appreciate that these systems are representative only and not limiting and may apply the principles and techniques of the present invention to a wide variety of wireless communication systems based on different access and modulation methods, given the teachings of the present description.

Figure 1 describes a wireless communication network 10. The network 10 includes a core network (CN) 12, communicatively connected to one or more other networks 14, such as the PSTN Public Exchange Telephone Network, by its acronym in English), the Internet, or similar. Communicatively connected to CN 12 there are one or more Radio Network Controllers (RNCs) 16, which in turn control one or more Node B 18 stations. Node B also known as a base station, includes the frequency equipment radio (RF) and the antennas necessary to perform the wireless radio communications with one or more user equipment (UE) 20 within a geographical region, or cell 22. As described, the Node B 18 transmits data and controls signals to the UE 20 in one or more downlink channels and UE similarly transmits data and controls signals to the Node B 18, in the uplink.

Interleaved within the data in the downlink transmission, the network 10 transmits reference symbols, also known in the art as pilot symbols, to help UE 20 carry out channel staging in the downlink channel responses . Figure 2A describes example of reference symbol resources for the LTE network 10 of Figure 1, when the Node B 18 transmits on a single antenna port. The subcarriers of grid graphs described in the axis of the ordinates (increasing the current frequency! Below) and time (increasing to the right) on the axis of the abscissas. Observe that the times are organized f? frames, with slots of even numbers and odd numbers described. Each grid element is a resource element of OFDM time-frequency that can carry out a data symbol, reference symbol, or none. Figures 2B and 2C describe transmissions of reference symbols when the Node B 18 transmits in two and four antenna ports, respectively.

The reference symbols allow UE to use a wide range of normal techniques to estimate the frequency responses of all subcarriers. Since the values of the reference symbols are known to the UE 20, the estimation quality is generally higher in the subcarriers occupied by the reference symbols.

Figure 3 describes a method for reporting CSIs by an UE 20 to the network 10, according to one modality. The UE 20 receives known reference symbols on some subcarriers transmitted to it, as described in Figure 2 (block 102). The UE 20 selects a group of separate subcarriers non-uniformly, in which the channel estimation for CSI feedback is carried out (block 104). In one embodiment, the selection of the subcarriers is limited to those in which the reference symbols are transmitted, because the channel estimation quality is generally higher in these subcarriers. However, in other embodiments, the UE 20 additionally selects one or more subcarriers that do not include reference symbols. As was also discussed in the present, the selection of separate subcarriers is not uniformly carried out according to a scheme that is synchronized in some way with the network. The UE 20 estimates the frequency response of the channel (block 106). The frequency response samples associated with the selected subcarriers are quantized or encoded by an appropriate source encoder in digital transfers (block 108). The digital transfers are then transmitted via an appropriate control channel from UE 20 to network 10 (block 110). The control channel provides adequate error detection and correction coding as well as radio resources (transmission power and frequency resource allocation) to ensure the proper reception quality in the network 10. The method is then repeated.; Figures 4A and 4B describe the frequency response of the representative channel for the in-phase (Figure 4A) and quadrature (Figure 4B) components of a received signal. These samples are described as stars in Figures 4A and 4B. The samples are not always on the frequency response curves due mainly to two sources of noise. First, it is assumed that the MSE square error of: UE channel estimator on the reference symbol subcarriers is -20 dB. Second, parts I and Q of the selected channel estimates are digitized independently by a simple 4-bit uniform quantizer. The resulting average quantization noise is approximately ~ 22 dB. With this setting, a total of 15 * 4 * 2 = 120 bits are fed again by the UE 20.

With uniform sampling, the Nyquist theorem dictates that samples (subcarriers) must be selected at twice the highest frequency of the channel frequency response curve to fully characterize the curve. Using non-uniform samples, however, quite smaller than the Nyquist criterion of subcarriers can be selected, with a high probability of accurate reconstruction of the frequency response curve of channels by network 10. Consequently, selected subcarriers separated non-uniformly, the UE 20 can fully characterize the channel and provide direct CSI feedback, without imposing excessive superiority on the uplink channel.

Upon receipt by network 10, the received CSI feedback bits are demodulated and quantized inversely. The full-frequency domain channel coefficients can be estimated by setting a time-domain pulse delay module based on the received subcarrier samples. Applying, e.g., a Fast Fourier Transform (FFT) to the estimated delay coefficients gives a response of frequency-domain very close to that described in Figures 4A and 4B. The detail of the CSI feedback network side process based on estimates of separate subcarrier channels are uniformly described in the U.S. Patent Application. co-pending Series No. 12 / 555,973, assigned to the assignee of the present application, filed concurrently herewith and incorporated herein by reference in its entirety. The side network process assumes that the network 10 is aware of which selected subcarriers are not uniformly analyzed by the UE 20. Therefore, the UE 20 should select the subcarriers separately, not uniformly according to a scheme, protocol or formula that it is synchronized with the network 10. There are numerous ways to achieve this.

In one embodiment, the set of separate subcarriers is not uniformly changed for each batch, or interaction, of the CSI feedback report, in a coordinated fashion with the network 10.

In one embodiment, the group of separate subcarriers are not uniformly selected based on pseudo-randomized indices that can be obtained by sequentially taking the indices produced by a pseudo-alatorios number generator. The number generator: pseudo-random can be calculated based on an algebraic modification of the input reading indexes. For example, algebraic modification can be based on quadratic permutation polynomials (QPP), as described in the 3GPP Technical Specifications 36.212. "Multiplexing and channel coding", incorporated herein by reference. As another example, the algebraic modification can be based on a finite field calculation.

As an example of pseudo-randomized indices with synchronized reading deviation, pseudo-randomized indices can be obtained by sequentially taking the indices produced by an interleaver. The interleaver can be calculated based on a rectangular arrangement interspersed with the columns, as described in section 5.1.4.2.1 of the 3GPP 36.212 Techniques Specifications.

As yet another example, the sequential reading of indexes can be synchronized between UE 20 and network 10 via a reading deviation of the corresponding index. The agreed reading rate deviation can be obtained in many ways. It can be transmitted explicitly in the same transport channel with the digital paths of the UE 20 to the network 10. Alternatively, the read-off of the indexed index can be implicitly calculated based on an identification number of UE 20, a subframe number, a batch of CSI feedback or interaction count, an antenna identification number, a network side identification number, or the control channel resource index of uplink (eg, where is the index of the first resource block for the uplink control channel). The agreed reading rate deviation can be implicitly calculated based on the downlink control channel resource index (e.g., where is the index of the first resource block for the downlink control channel). Alternatively, the agreed read rate deviation can be transmitted from the network 10 to the UE 0 before the UE 20 leading to the channel estimate or it can be previously agreed between the network 10 and the UE 20. In any case, the deviations of index reading can be stored in UE 20 as a search table.

In one example, the group of repaired subcarriers is not uniformly selected by initially choosing uniformly separated subcarriers and then applying pseudo-randomized hesitation, with a key synchronized to the network 10, to the subcarriers evenly spaced to generate the group of separate subcarriers non-uniformly. In one embodiment, the maximum extension of the pseudo randomized hesitancy is selected to be less than the uniform separation in the uniformly separated indices. The generation of pseudo randomized hesitation can be calculated based on algebraic modification of an input key. As described above with respect to the selection of non-uniform subcarriers, the pseudo-randomized hesitation can be obtained by sequentially taking the indices produced by an itnercalator or a pseudorandom number generator, with the generation of the indices calculated by UE 20 based on any of the above factors, or communicated among the network 10 and UE 20, as also described above.

A more general formulation of the subcarrier selection, quantification channel estimation and CSI feedback report are now presented. The frequency response of a channel at frequency f and time t can be expressed in terms of the domain channel pulses h (l; t) having delays t, as follows: i \ H (f; t) = h; t) ej2n £ ti In each report interaction or time t, the following steps were carried out by UE 20: First, UE 20 forms an estimate of the downlink anal in a number of subcarriers. As described above, the known reference signals are transmitted from each network antenna (see Figure 2A-2C) and UE 20 can use these reference signals to form a channel estimate on a number of subcarriers using normal techniques. These estimates are denoted by the following vector Nxl: g (t) = [H (fi; t) H (f2; t) ... H (fN; f)] T Where ñ (f; t) is the estimated frequency response of UE of the channel at frequency f and time t.

Second, for each reporting instant, UE 20 forms a number of linear combinations of elements of g (l), that is, UE 20 multiplies the vector g (t) by a mixed matrix P (t), of size MxN, for obtain a new vector r (t) of size Mxl, according to : r (t) = P (f) x g (t).

In the modalities where the elements of P (t) comprise only the values zero or one, P (f) "selects" elements of the vector of channel estimates of nonunifiable subcarriers g (t) according to each row of P ( t). In some embodiments, the results of calculations or communications described above for selecting the reading deviations of pseudo-randomized indices can be stored in the mixing matrix P (t). In more general modalities, however, the elements of P (t) are not restricted to values of zero or one. For example, the elements may comprise fractional values between zero and one, in which c $ s act as weight factors as well as selectors. Additionally, the elements may comprise complex values.

The mixed hue P (t) can change for different groups of CSI feedback interactions. In one embodiment, the selection of P (t) may be an orderly selection from a collection of mixing matrices. In one embodiment, the change of P (t) may comprise selecting different row compositions. For example, the selection of different row compositions can be based on the orderly use of a plurality of rows. As another example, it can be based on a pseudo-randomized selection of a plurality of rows. The pseudo-randomized selection of rows can be obtained by sequentially taking the indices produced by an interleaver or pseudo-random number generator, wherein the indices can be communicated or calculated in any manner described above.

In one embodiment, the mixing matrix P (t) comprises rows having at least one element without zero. In another embodiment, the mixing matrix P (t) comprises rows given by an orthonormal matrix, such as a Hadamard matrix. In yet another embodiment, the mixing matrix P (t) comprises rows given by a unitary matrix. In yet another mode, the mixing matrix P (t) can be generated first by generating pseudo-random matrices. { Af} with entries distributed by independent Gausina, carrying $ a decomposition in each Af and using each resulting Q Unitary matrix as a candidate for P (t).

However, the mixing matrix P (t) is derived, after multiplication with g (t), the elements of the product matrix r (t) are quantized using a quantizer Qv (.) To obtain a number of bits , denoted as the vector b (f), representing the vector r (t). The bits in b (t) are transmitted to the network 10 using an uplink control channel. As is known in the art, the transmission process may include addition redundancy such as CRC, FEC and the like, to ensure reliable transmission to the network 10.

In the embodiments described above, the UE 20 determines the parameters for selecting non-sequential subcarriers and / or faded parameters to generate a non-sequential selection of subcarriers, such as the selection of indices for pseudo-random number generator, autonomously or almost autonomously from the network 10 (although, give then, whenever the selection mechanism is used, it must be synchronized with the network 10). In some embodiments, however, network 10 directly controls these and other parameters via transmissions to UE 20 in the downlink.

In one embodiment, the network 10 determines the: group of subcarriers (flf fN), for which the UE 20 must estimate the channel response and place in the vector g (t). In one embodiment, the network 10 determines the mixing matrix P (t) that the UE 20 must use in each report case. In one embodiment, the network 10 determines the quantizer Qf (.) That the UE 20 uses in each report case, which determines, for example, how many bits are used to quantify each element of r (t). In one embodiment, network 10 determines the frequency in which CSI feedback reports should be transmitted by UE 20 in the uplink. In all these modalities, the network 10 communicates the relevant determinations to the UE 20 in the downlink communications. Additionally, of course, the network 10 schedules the time frequency uplink resources in which the CSI feedback reports should be transmitted over UE 20, just as for any uplink communication.

In a typical network 10, each UE 20 must have to report CSI feedback on multiple downlinks, of multiple different Bs 18 nodes. Since the path loss between each UE 20 and Node £ 18 is different, the downlink channels that will be estimated and reported with each UE 20 will have different average power. With a fixed transfer rate budget for the CSI 1 feedback assigned to each UE 20, a problem arises as to how the 'Speed The total fixed reference shall be divided among different downlink channels observed by UE 20.

If a channel between a given UE 20 may have to report CSI feedback on multiple downlink channels, from multiple different Bs 18 nodes, the downlink channels will be stowed and reported by each UE 20 which will have different average power. With a fixed budget rate for CSI feedback allocated to each UE 20, a problem arises as to how the fixed transfer rate should be divided among different downlink channels observed by UE 20.

If a channel between a given UE 20 and a given Node B 18 is extremely weak, the signals transmitted from Node B 18 will have very little impact on the UE 20 receiver. Therefore, there is little need for UE 20 to report feedback from CSI corresponding to channels that are very weakly received in UE 20. Consequently, in one embodiment, UE 20 allocates a larger portion of the CSI feedback transfer rate allocated to the downlink channels! Which are relatively strong, which the channels that are relatively weak. Given a group of average channel signal resistances g (l), q (2) g (N) and a total CSI feedback allowance of K bits, the network! 10 can assign your total transfer speed budget between different channels. In one embodiment, network 10 carries out the allocation in accordance with the Breiman, Friedman, Olshen and Stone (BFOS) Generalized Algorithm, as described by EA Riskin in the document, "Optimal Bits Assignment via Generalized BFOS Algorithm" , published in IEEE Trans. Info. Theory, 1991, the description of which is hereby incorporated by reference in its entirety.

In one embodiment, the CSI feedback report can be dispersed over a plurality of CSI feedback interactions. That is, a group of separate subcarriers are not uniformly selected and a frequency response is calculated for each subcarrier. The frequency responses are quantified. However, instead of transmitting all the frequency response data to the network one at a time, the report is disseminated on two or more CSI feedback interactions. For example, at time N, some number, eg, ten, subcarriers are selected and their frequency responses calculated and quantified (possibly together). The quantized transfers can be transmitted to the network over the next ten time intervals, e.g., at times N + l, N + 2, N + 10. Of course, reports for two subcarriers can be transmitted at one time, using five CSI report intervals, or any other exchange. East report method reduces the uplink bandwidth required to report CSI captured in a while.

In another modality, a persistent form of the CSI report comprises selecting one or more subcarriers and calculating their frequency response. The quantized frequency response is transmitted to the network. Over time, the selection of subcarriers is non-uniform. For example, a first subcarrier is selected at time N and its quantized frequency response is transmitted to the network in the reporting interval N + l. At this time, a new sub-carrier (on a different frequency) is selected and its quantized frequency response is transmitted to the network in the reporting interval N + 2. Similarly, two or more subcarriers may be selected during any given CSI generation in the reporting interval. This reporting method reduces the bandwidth of the uplink by dispersing the selection of subcarriers and the data $ of CSI quantified over time.

The modalities described herein significantly reduce the CSI feedback bandwidth, while allowing the availability of CSI to the network to be precise. This efficiently allows the implementation of advanced network protocols such as splicing process in multiple point transmission in the coordinates, without consuming excess uplink transmission resources.

The present invention, of course, can be carried out in other ways than those specifically exhibited herein without departing from the essential features of the invention. The present modalities will be considered in all aspects as illustrative and not restrictive and all changes arising within the range of meaning and equivalence of the appended claims are intended to be embraced herein.

Claims (20)

1. - A method for reporting channel status information (CSI) by the user equipment (UE) operating in a wireless communication network in which the downlink data is modulated into a plurality of subcarriers, each having a frequency different, understanding, in each interaction: receiving a plurality of known reference symbols on a subgroup of the plurality of subcarriers; selecting a group of separate subcarriers non-uniformly using a selection scheme synchronized to the network; , estimating a frequency response for each selected subcarrier; quantifying the frequency responses;: and transmitting the quantized frequency responses to the network via an uplink control channel.

2. - The method of claim 1, wherein the selected subcarriers include one or more reference symbols.

3. - The method of claim 1, wherein the selection of a group of separate subcarriers does not uniformly corresponds to select a different group of separate subcarriers are uniformly for each CSI reporting interaction.

4. - The method of claim 1, wherein the selection of a group of separate subcarriers non-uniformly using a selection scheme synchronized to the network comprises selecting the group based on pseudo-randomized indices with an index reading deviation synchronized to the network .

5. - The method of claim 4, wherein the pseudo-randomized indices comprise the sequential indices produced by an interleaver and a pseudo-random number generator.

6. - The method of claim 5, wherein the sequential indexes are synchronized between UE and the network by a predetermined index deviation.

7. - The method of claim 1, wherein the transmission of the quantized frequency responsive to the network via an uplink control channel comprises transmitting less than the entire group of frequency responses quantized in a CSI interaction.

8. - The method of claim 1, wherein the selection of a group of separate subcarriers non-uniformly using a selection scheme synchronized to the network comprises: select a group of separate subcarriers uniformly, and apply pseudo-random blur, generated using a key synchronized to the network, to the group of subcarriers evenly spaced to generate $ 1 group of separate subcarriers non-uniformly.

9. - The method of claim 8, wherein the pseudo-random blur is obtained from the sequential indices produced by one of an interleaver and a pseudo-random number generator.

10. - The method of claim 9, wherein the sequential indexes are synchronized between UE and the network by a predetermined index offset.

11. - A method for reporting the channel state information (CSI) by the user equipment (UE) Operating in a wireless communication network in which the downlink data is modulated in a first plurality of subcarriers, each having a different frequency, understanding, in each interaction: receiving a plurality of known reference symbols on a subgroup of the first plurality of subcarriers; estimating a frequency response for each of a second plurality of subcarriers; : collecting the frequency responses in a vector; selecting a group of frequency responses by multiplying the frequency response vector by a mixed matrix that is synchronized to the network, to give a vector of selected frequency responses; quantify the selected frequency responses; Y transmit the quantized frequency responses to the network via an uplink control channel.

12. - The method of claim 11, wherein the mixing matrix changes to face CSI report interaction.

13. - The method of claim 12, wherein, for each interaction, a different spinneret composition is selected for the mixed matrix.

14. - The method of claim 13, wherein the swath composition is selected by a pseudo-random selection from a collection of predetermined swaths.

15. - The method of claim 14, wherein the pseudo-random row selection is obtained from the sequential indices produced by one of an interleaver and a pseudo-random number generator.

16. - The method of claim 15, wherein the sequential indexes are synchronized between the UE and the network by a predetermined index offset.

17. - The method of claim 15, wherein the mixing matrix is a unitary matrix.

18. - The method of claim 17, wherein the mixing matrix is formed by: the generation of a plurality of pseudo-random matrices with entries distributed by independent Gaussian; carry out a QR decomposition in each random matrix to generate a unitary matrix; Y select a unitary matrix as the mixing matrix.

19. - The method of claim 11, wherein the selection of a frequency response group by multiplying the frequency response vector, by a mixing matrix that is synchronized to the network comprises: receive from the network an indication of the mixing matrix to be used, and multiply the frequency response vector by the indicated mixing matrix.

20. - A User Equipment (UE) operative in a wireless communication network in which the downlink data is modulated in a plurality of subcarriers, each having a different frequency, comprising: one or more antennas; selection means for choosing a group of subcarriers using a selection scheme synchronized with the network; an operating frequency estimator for estimating a frequency response for selected subcarriers; an operational quantifier to quantify selected frequency responses, and an operational transmitter for transmitting selected quantized frequency responses to the network via an uplink control channel.